Why does lithium battery become a bomb?

From a chemical point of view, there are many reasons for the explosion of lithium batteries, and a considerable part of the reasons have a lot to do with the manufacturer's design flaws. As we all know, a major cause of battery explosion is the short circuit of the battery (that is, there are no electrical appliances in the circuit where the battery is located, and the phenomenon of excessive current passing through the battery in a short period of time), regardless of whether it is a short circuit or an overcharge (a lithium battery explodes) Another important cause of this is that the battery charging voltage is higher than its set upper limit), which will cause a large amount of heat and gas to accumulate in the lithium battery in a short period of time (the lithium battery generates gas when it is working). In this way, in order to release the pressure, the lithium battery will either activate the internal pressure release device, or it will crack the shell straightly. Both of these situations will cause the internal material of the battery to directly contact the air and burn. Generally speaking, the explosion and combustion of lithium batteries are rarely caused by external circuit failures, which means that most of the explosion and combustion events of lithium batteries are caused by design defects inside the battery. For example, in the aforementioned Sony laptop battery explosion incident, metal impurities were detected in the electrolyte part of the problem battery. The accident was also due to the unexpected conduction caused by the metal impurities, forming an internal short circuit and causing an explosion. of. Coincidentally, the fire incident on the lithium battery of the Boeing 787 aircraft was also related to the significant drop in the electrolyte performance of the aircraft battery in a special environment, which induced an internal short circuit. Of course, the two explosions of lithium batteries involved traditional lithium batteries, and the protagonist in the explosion of Samsung Galaxy Note 7 was lithium ion polymer batteries, so lithium ion polymer batteries are in this category. What is special about the incident? In fact, generally speaking, because lithium-ion polymer batteries do not have a hard shell, the possibility of violent explosion and combustion has been greatly reduced. In the event of an explosion accident, such batteries will explode ahead of time due to the poor impact resistance of the shell. So it usually manifests as slow burning after explosion. However, the high degree of variability in the shape of lithium-ion polymer batteries can not only give equipment manufacturers more free design space, but also often require additional designs for battery packs. In this way, it is inevitable that the battery pack design fails to pass, which will cause an accident. In the Samsung Galaxy Note 7 explosion, it has been preliminarily determined that the battery pack with major defects in the processing technology is likely to be the culprit of the explosion. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.